Sexual assault is a major concern on the U.S. college campus. Engaging students as pro-social bystanders has become more common as a potentially effective mechanism for reducing the incidence of sexual assault and mitigating the harm of assaults that have already occurred. Understanding the influences of pro-social bystander behavior is imperative to developing effective programs, and the use of an evidence-based theoretical framework can help identify the differences between students who intervene and those who do not when presented with the opportunity. A sample of 815 undergraduate university students completed the Sexual Assault Bystander Behavior Questionnaire, a survey based on the theory of planned behavior (TPB) that investigates students' perceived behavioral control to intervene, subjective norms that support intervening, attitudes toward intervening, and intent to intervene in the future. Two-tailed t tests revealed interveners reported significantly greater perceived behavioral control than non-interveners for eight of the 12 intervention behaviors, more supportive subjective norms than non-interveners for seven of the 12 intervention behaviors, more positive attitudes than non-interveners for only one of the 12 intervention behaviors, and greater intent to intervene in the future for six of the 12 intervention behaviors. Differences in the four TPB variables were not consistent for the 12 intervention behaviors. The use of a theoretical framework found to be effective in explaining-and changing-other health-related behaviors, and the inquiry into students' opportunities to intervene to compare against their reported intervention behaviors, is new to this body of literature and contributes to the understanding of the influences of pro-social bystander behavior.